[usage of box type mechanical filter]

1) Filter material treatment: quartz sand or anthracite shall be used as filter material, and chemical stability test of acid, alkaline and neutral solution shall be carried out for filter material. After soaking for 2-4 hours, the following requirements shall be met: · the increase of total solids shall not exceed 20mg / L; · the increase of oxygen consumption shall not exceed 10mg / L; · the increase of silicon dioxide shall not exceed 10mg / L after soaking in alkaline medium.

2) Filter material loading: the factory with hydraulic loading and unloading shall use hydraulic loading. After loading, the manhole shall be closed for backwashing until the effluent is clarified, then the manhole shall be opened to remove the powder and dirt on the upper part, and the surface of filter material shall be leveled. If the backwashing is conducted twice, the effluent is qualified after the effluent is clarified. If manual loading is adopted, about 1 / 2 of water shall be loaded in the equipment first, and the filter material shall be loaded in three times, each time 1 / 3 of filter material shall be loaded and backwashed, and the final requirement is the same as that of hydraulic loading and unloading.

3) Filtration: before putting into operation, it is necessary to wash the water until the water is clarified. Observe the water once an hour. If the water quality fails to meet the requirements, stop immediately and backwash, or determine the backwash according to the pressure difference between the inlet and outlet. Generally, the head loss of the filter layer increases about 0.05Mpa compared with the clean filter material layer.

4) Backwashing: close the water inlet valve, open the drain valve, lower the water surface to the position of the mirror pipe, close the drain valve, open the compressed air inlet valve and the exhaust valve, send the compressed air from the bottom, loosen the filter layer for 3-5 minutes, and then the gas is discharged from the exhaust valve. Slowly open the backwashing water inlet valve, and the water enters from the bottom. When the exhaust valve overflows, immediately close the exhaust valve, open the backwashing drainage valve, and the water will be discharged from the upper part, and the flow will gradually increase. Finally, maintain a certain backwashing strength, make the filter expand by 10% - 15%, keep for 2-3 minutes, close the compressed air inlet valve, and increase the backwashing flow, so that the filter expand by 40% - 50%, keep for 1-2 minutes Minutes, then close the backwash inlet valve and backwash drain valve.

5) Washing: during washing, open the water inlet valve and washing drain valve, wash the water from top to bottom. The washing flow rate is 5 m / h, washing for 5-10 minutes. When the water is transparent, close the drain valve, open the water outlet valve and put it into normal operation.

6) When washing the mechanical filter, attention shall be paid: there shall be no sand running during backwashing. In case of the abnormal phenomenon that the backwashing time exceeds the specified value and the water outlet is still unclear, the equipment shall be overhauled instead of increasing the backwashing speed as much as possible to avoid damaging the water supply treatment equipment.